High energy fuel



United States Patent HIGH ENERGY FUEL Filed Apr. 7, 1958, Ser. No. 726,654

4 Claims. (Cl. 52.5)

No Drawing.

This invention relates to high energy fuel and to a method of enhancing the energy content of a low viscosity hydrocarbon liquid.

The importance of high energy fuel has increased considerably with the development of jet and rocket engines. To develop high speeds and high thrusts with rocket and jet engines, high energy fuel is essential. In addition to the high energy content, the fuel must be stable, and preferably non-corrosive. Also it must be such that it can be easily stored, handled, and capable of being metered into the combustion chamber of the engine Without the need of complicated mechanical devices.

It is, therefore, an'object of this invention to provide a fluid high energy fuel which has the above requirements and is suitable for jet and rocket engines on other engines requiring a high energy fuel. A further object is to provide a method for enhancing the energy content of a low viscosity hydrocarbon liquid.

The above objects are attained by dispersing in a low viscosity hydrocarbon liquid particles of magnesium hydride having an average particle size of less than one micron. By dispersing the small particles of magnesium hydride in a low viscosity hydrocarbon liquid, a high energy fuel is obtained which burns with intense heat and is readily adaptable for use as a rocket or jet engine fuel. Fuels containing up to 60 weight percent of magnesium hydride may be thus prepared which are fluid and can be pumped at temperatures below 40 C. These dispersions are stable and may be safely handled and pumped.

The term low viscosity hydrocarbon liquid, as used herein, means petroleum fractions having a gravity in the range of 30 to 82 A.P.I., such as gasoline, kerosene, diesel fuel, and other petroleum fraction fuels being used as jet fuels at present.

The high energy fuel according to the invention comprises substantially a low viscosity hydrocarbon liquid and fine particles of magnesium hydride dispersed therein. The amount of the magnesium hydride dispersed in the hydrocarbon liquid may be from 20 to 60 weight percent. Dispersions containing from 30 to 50 weight percent of the magnesium hydride in a petroleum fraction having a gravity in the range of 35 to 50 A.P.I. are especially suitable for jet engine fuel.

In the highly concentrated dispersions, containing over 30 weight percent of magnesium hydride, a dispersant is added which is soluble in the low viscosity hydrocarbon liquid and capable of adsorption on surface of the magnesium hydride particles, such as sorbitan esters as monolaurate, monooleate, and trioleate, substituted oxazoline, and the like. The addition of a dispersant appreciably lowers the viscosity of the dispersion especially when the dispersion is in high concentration. The dispersant does not have any deleterious effect upon the combustibility of the fuel and thus may be also used in a low concentration dispersion to obtain a reduction in its viscosity. The amount of the dispersant added is generally from Patented Nov. 15, 1960 1 to 10 weight percent of the magnesium hydride. A preferred amount is from 4 to 6 weight percent.

Generally, the average size of the particles of magnesium hydride dispersed in the low viscosityhydrocarbon liquid is less than one micron and preferably in the range of 0.1 to 0.5 micron. Magnesium hydride is friable and may be readily reduced to the desired fine particle size by grinding. It may be comminuted, as in a ball mill, in a dry state under an inert atmosphere, such as hydrogen, nitrogen, argon or may be wet ground in the presence of an inert liquid. Although any inert liquid may be used as a grinding fluid, the low viscosity hydrocarbon liquid which is to be employed as one of the components of the high energy fuel is most often used. For example, if the high energy fuel is to consist of kerosene and the magnesium hydride, kerosene is employed. Thus, the grinding and mixing operations are combined and the productobtained after the grinding operation is the high energy fuel desired. Unless a fuel having a higher concentration of magnesium hydride is desired, approximately equal weights of the magnesium hydride and the hydrocarbon fuel are used in the ballmilling operation. The final product obtained from the ball mill may be diluted with additional low viscosity hydrocarbon liquid if a fuel containing less magnesium hydride is desired.

If an inert liquid other than the low viscosity hydrocarbon liquid component is used as the grinding fluid, a volatile liquid, such as hexane, butane, or ethane, having a boiling point below the thermal decomposition temperature of the magnesium hydride is employed. After the grinding operation, the mixture is heated or pressure released depending on the liquid used and the magnesium hydride is separated from the grinding fluid by vaporization of the grinding fluid. A dry free-flowing product is obtained which may be then intermixed with the desired low viscosity hydrocarbon liquid.

Although not essential to the grinding operation, the dispersants previously described may be added to the grinding fluid. Presence of the dispersant in the grinding medium aids in the grinding and less time is required to obtain the desired particle size than when a dispersant is not used.

A gelling agent, such as aluminum octoate, aluminum stearate, lithium stearate, and magnesium octoate, may also be added to the high energy fuel to aid in maintaining the particles of magnesium hydride in suspension. This is especially advantageous if the fuel is to be stored for a considerable length of time. The amount of gelling agent used is small being in the range of from 0.5 to about 2.5 Weight percent of the magnesium hydride content. It is preferred to use about 1 to 2.0 weight percent. By using less than 2.5 Weight percent of the gelling agent, based on the magnesium hydride content, the amount is insuflicient to gel the mixture or increase its viscosity but is effective in decreasing the settling of the magnesium hydride.

The magnesium hydride may be readily prepared if desired from relatively pure magnesium. Magnesium particles which pass through 200 standard sieve mesh or lathe turnings of around 0.002 inch thick react readily with hydrogen to form the metal hydride. In preparing the hydride, articles of the metal or the turnings are placed in a reactor which is then pressurized with hydrogen to a pressure in the range of 255 to 4,000 pounds per square inch or higher and heated to a temperature of 400 to 600 C. At a reaction temperature of 400 C, and a pressure of 4,000 pounds per square inch, the reaction of the metal with hydrogen is very rapid, taking about one minute for completion. At lower temperatures and pressures, the reaction is slower and may require as long as ten hours for completion. The product thus obtained may then be charged into a ball mill, Without any further size reduction, and ground to the desired fineness.

As an example illustrative of the invention, a high energyfuel was prepared containing approximately 50 Weight percent of magnesium hydride in jet engine fuel which is referred to in U.S. Government Specifications as JP-4. In this example a bar of relatively pure magnesium was machined on a lathe to form 20 pounds of lathe turnings having a thickness of approximately 0.002 inch. The magnesium turnings thus obtained were placed in a closed reactor which was pressurized With hydrogen to a pressure of 4000 pounds per square inch and heated to a temperature of approximately 500 C. for a length of time of about two minutes. A substantially quantitative yield of magnesium hydride was thus obtained. A portion (2500 gm.) of the magnesium hydride thus obtained was placed in a steel ball mill containing stainless steel balls and sufiicient amount of the jet engine fuel was added so that the mixture contained approximately 50 percent of magnesium hydride. Sorbitan monolaurate, as dispersant, and aluminum octoate were added to the magnesium hydride-jet fuel mixture in amounts of 250 gm. and 62.5 gm respectively prior to the mixing and grinding. The ball mill was operated for 24 hours which reduced the particle size of the magnesium hydride to approximately 0.3 micron. The slurry was removed from the ball mill. The high energy fuel thus obtained was non-corrosive and burned with intense heat. The product was stored for 180 days and practically no settling of the magnesium hydride was obtained,

What is claimed is:

1. A high energy fluid fuel, consisting essentially of a low viscosity hydrocarbon liquid and magnesium hydride dispersed in said hydrocarbon liquid as particles having an average particle size of less than one micron in an amount of from 20 to 60 weight percent.

2. A high energy fiuid fuel, consisting essentially of a low viscosity hydrocarbon liquid having a gravity in the range of to A.P.I., magnesium hydride having an average particle size in the range of 0.1 to 0.5 microns dispersed in said hydrocarbon liquid in an amount of 30 to 50 weight percent, and a dispersant selected from the group consisting of sorbitan monolaurate, sorbitan monooleate and sorbitan tioleate dissolved in said hydrocarbon liquid in an amount of 1 to 10 weight percent of the magnesium hydride.

3. A process for enhancing the energy content of a low viscosity hydrocarbon liquid, which comprises dispersing in said hydrocarbon fuel particles of magnesium hydride having an average particle size less than one micron in an amount of from 20 to weight percent.

4. A process for enhancing the energy content of a low viscosity hydrocarbon liquid, which comprises dispersing in the hydrocarbon liquid particles of magnesium hydride having an average particle size in the range of 0.1 to 0.5 micron in an amount of from 30 to 50 weight percent, said hydrocarbon liquid having dissolved therein a dispersant selected from the group consisting of sorbitan monolaurate, sorbitan monoolc'ate and sorbitan trioleate in said hydrocarbon liquid in an amount of from 1 to 10 weight percent of the magnesium hydride.

References Cited in the file of this patent UNITED STATES PATENTS 2,771,739 Malina et al. Nov. 27, 1956 2,782,592 Kolfenbach et al Feb. 26, 1957 2,890,108 Toulmin June 9, 1959 

2. A HIGH ENERGY FLUID FUEL, CONSISTING ESSENTIALLY OF A LOW VISCOSITY HYDROCARBON LIQUID HAVING A GRAVITY IN THE RANGE OF 35 TO 50* A.P.I., MAGNESIUM HYDRIDE HAVING AN AVERAGE PARTICLE SIZE IN THE RANGE OF 0.1 TO 0.5 MICRONS DISPERSED IN SAID HYDROCARBON LIQUID IN AN AMOUNT OF 30 TO 50 WEIGHT PERCENT, AND A DISPERSANT SELECTED FROM THE GROUP CONSISTING OF SORBITAN MONOLAURATE, SORBITAN MONOOLEATE AND SORBITAN TOILEATE DISSOLVED IN SAID HYDROCARBON LIQUID IN AN AMOUNT OF 1 TO 10 WEIGHT PERCENT OF THE MAGNESIUM HYDRIDE. 